Method of manufacturing a magnetic recording medium with a laser textured data zone

ABSTRACT

The substrate of a magnetic recording medium is laser textured using a continuous wave laser light beam and microfocusing lens system to form a laser textured data zone comprising a plurality of substantially uniform concentric microgrooves. A suitable microfocusing lens system includes an array of horizontally and vertically spaced apart microfocusing lenses, each optically linked to a fiber optic cable.

RELATED APPLICATIONS

This application is a divisional of application Ser. No. 08/972,229 nowU.S. Pat. No. 6,021,032 filed Nov. 17, 1997.

This application claims priority from provisional patent applicationSer. No. 60/037,627, filed Jan. 15, 1997, the entire disclosure of whichis hereby incorporated by reference herein.

This application is a continuation-in-part application of U.S. patentapplication Ser. No. 08/955,448, filed Oct. 21, 1997, now pending,which, in turn, is a continuation-in-part of U.S. patent applicationSer. No. 08,954,585, filed on Oct. 20, 1997 now U.S. Pat. No. 5,952,058.The entire disclosure of U.S. patent application Ser. No. 08/955,448 andthe entire disclosure of U.S. patent application Ser. No. 08,954,585 nowU.S. Pat. No. 5,952,058 are hereby incorporated by reference herein.

Some of the subject matter disclosed in this application is similar tosubject matter disclosed in application Ser. No. 08/919,601 (now U.S.Pat. No. 5,837,330) filed on Aug. 28, 1997.

TECHNICAL FIELD

The present invention relates generally to laser texturing a magneticrecording medium. The present invention is particularly applicable tolaser texturing a substrate for a high areal recording density magneticrecording medium.

BACKGROUND ART

Conventional magnetic disk drive designs comprise a commonly denominatedContact Start-Stop (CSS) system commencing when the head begins to slideagainst the surface of the disk as the disk begins to rotate. Uponreaching a predetermined high rotational speed, the head floats in airat a predetermined distance from the surface of the disk due to dynamicpressure effects caused by air flow generated between the slidingsurface of the head and the disk. During reading and recordingoperations, the transducer head is maintained at a controlled distancefrom the recording surface, supported on a bearing of air as the diskrotates, such that the head can be freely moved in both thecircumferential and radial directions allowing data to be recorded onand retrieved from the surface of the disk at a desired position. Uponterminating operation of the disk drive, the rotational speed of thedisk decreases and the head again begins to slide against the surface ofthe disk and eventually stops in contact with and pressing against thedisk. Thus, the transducer head contacts the recording surface wheneverthe disk is stationary, accelerated from the stop and duringdeceleration just prior to completely stopping. Each time the head anddisk assembly is driven, the sliding surface of the head repeats thecyclic operation consisting of stopping, sliding against the surface ofthe disk, floating in the air, sliding against the surface of the diskand stopping.

It is considered desirable during reading and recording operations tomaintain each transducer head as close to its associated recordingsurface as possible, i.e., to minimize the flying height of the head.Thus, a smooth recording surface is preferred, as well as a smoothopposing surface of the associated transducer head, thereby permittingthe head and the disk to be positioned in close proximity with anattendant increase in predictability and consistent behavior of the airbearing supporting the head. However, if the head surface and therecording surface are too flat, the precision match of these surfacesgives rise to excessive stiction and friction during the start up andstopping phases, thereby causing wear to the head and recording surfaceseventually leading to what is referred to as a “head crash. ” Thus,there are competing goals of reduced head/disk friction and minimumtransducer flying height.

Conventional practices for addressing these apparent competingobjectives involve providing a magnetic disk with a roughened surface toreduce the head/disk friction by techniques generally referred to as“texturing.” Conventional texturing techniques involve polishing thesurface of a disk substrate to provide a texture thereon prior tosubsequent deposition of layers, such as an underlayer, a magneticlayer, a protective overcoat, and a lubricant topcoat, wherein thetextured surface on the substrate is intended to be substantiallyreplicated in the subsequently deposited layers.

The escalating requirements for high areal recording density imposeincreasingly greater requirements on thin film magnetic media in termsof coercivity, coercivity, squareness, low medium noise and narrow trackrecording performance. In addition, increasingly high density andlarge-capacity magnetic disks require increasingly smaller flyingheights, i.e., the distance by which the head floats above the surfaceof the disk in the CSS drive. The requirement to further reduce theflying height of the head challenges the limitations of conventionaltechnology for controlled texturing to avoid head crash.

Conventional techniques for providing a disk substrate with a texturedsurface comprise a mechanical operation, such as polishing. In texturinga substrate for a magnetic recording medium, conventional practicescomprise mechanically polishing the surface to provide a data zonehaving a substantially smooth surface and a landing zone characterizedby topographical features, such as protrusions and depressions. See, forexample, Nakamura et al., U.S. Pat. No. 5,202,810. Conventionalmechanical texturing techniques, however, are attendant with numerousdisadvantages. For example, it is extremely difficult to provide a cleantextured surface due to debris formed by mechanical abrasions. Moreover,the surface inevitably becomes scratched during mechanical operations,which contributes to poor glide characteristics and higher defects. Suchrelatively crude mechanical polishing, with attendant non-uniformitiesand debris, does not provide a surface with an adequately specularfinish or with adequate microtexturing to induce proper crystallographicorientation of a subsequently deposited magnetic layer on which torecord and read information, i.e., a data zone.

Data zones are conventionally provided with a smooth specular finish orwith a mechanically textured surface. In mechanically texturing asubstrate surface for data recordation and reading, i.e., a data zone,deep scratches are formed for inducing a desired magnetic orientation.However, mechanical texturing disadvantageously results in non-uniformscratches believed to be due to non-uniform particle sizes of abrasivematerial ranging from about 0.1 μm to about 5 μm. In addition, variousdesirable substrates are difficult to process by mechanical texturing.This undesirably limiting facet of mechanical texturing, virtuallyexcludes the use of many materials for use as substrates.

Laser technology has been employed to texture a substrate surface toform a topography suitable for a landing zone. Such landing zone lasertechnology typically comprises impinging a pulsed, focused laser lightbeam on a non-magnetic substrate surface. Laser textured landing zonestypically exhibit a topographical profile comprising a plurality ofspaced apart protrusions extending above the substrate surface or aplurality of spaced apart depressions extending into the substratesurface. See, for example, Ranjan et al., U.S. Pat. No. 5,062,021,wherein the disclosed method comprises polishing an NiP plated Alsubstrate to a specular finish, and then rotating the disk whiledirecting pulsed laser energy over a limited portion of the radius, toprovide a textured landing zone leaving a specular data zone. Thelanding zone comprises a plurality of individual laser spotscharacterized by a central depression surrounded by a substantiallycircular raised rim.

Another laser texturing technique is reported by Baumgart et al. “A NewLaser Texturing Technique for High Performance Magnetic Disk Drives,”IEEE Transactions on Magnetics, Vol. 31, No. 6, pp. 2946-2951, November1995. See, also, U.S. Pat. Nos. 5,550,696 and 5,595,791

In copending application Ser. No. 08/666,374 filed on Jun. 27, 1996 alaser texturing technique is disclosed employing a multiple lensfocusing system for improved control of the resulting topographicaltexture. In copending application Ser. No. 08/647,407 filed on May 9,1996, a laser texturing technique is disclosed wherein a pulsed, focusedlaser light beam is passed through a crystal material to control thespacing between resulting protrusions.

In copending PCT application Ser. No. PCT/US96/06830, a method isdisclosed for laser texturing a glass or glass-ceramic substrateemploying a laser light beam derived from a CO₂ laser source. Thetextured glass or glass-ceramic substrate surface comprises a pluralityof protrusions which extend above the substrate surface, withoutsurrounding valleys extending substantially into the substrate as ischaracteristic of a laser textured metallic substrate. The effect oflaser parameters, such as pulse width, spot size and pulse energy, andsubstrate composition on the protrusion or bump height of a lasertextured glass or glass-ceramic substrate is reported by Kuo et al., inan article entitle “Laser Zone Texturing on Glass and Glass-CeramicSubstrates,” presented at The Magnetic Recording Conference (TMRC),Santa Clara, Calif., Aug. 19-21, 1996.

In copending application Ser. No. 08/796,830 filed on Feb. 7, 1997, amethod is disclosed for laser texturing a glass or glass-ceramicsubstrate, wherein the height of the protrusions is controlled bycontrolling the quench rate during resolidification of the laser formedprotrusions. One of the disclosed techniques for controlling the quenchrate comprises preheating a substrate, as by exposure to a first laserlight beam, and then exposing the heated substrate to a focused laserlight beam.

As areal recording density increases the flying height must be reducedaccordingly, thereby challenging the limitations of conventional lasertexturing technology for uniformity and precision in forming a texturedlanding zone comprising a plurality of protrusions. The requirements forcontinuous alignment and adjustment of a laser beam are exacerbated ingeographic locations with relatively unstable environmental conditions,such as temperature, vibration and shock, particularly in regionssusceptible to seismological disturbances such as tremors andearthquakes. Conventional laser delivery systems for texturing a landingzone comprise a system of mirrors and lenses which must be precisely andaccurately maintained, particularly as the flying height is reduced to alevel of less than about 300 Å, due to inherent undulations of thesubstrate surface. Uniform and precise texturing require continuousmaintenance of alignment of a system of mirrors and lenses. It isextremely difficult to maintain the requisite precise alignment andsatisfy the reduced flying height requirements for high areal recordingdensity, particularly in geographical locations subjected toenvironmental changes, and seismological disturbances.

In copending application Ser. No. 08/954,585, filed on Oct. 20, 1997 nowU.S. Pat. No. 5,952,058, an apparatus and method are disclosed for lasertexturing a substrate employing a fiber-optic laser delivery systemwherein sub-laser beams are passed through plural fiber optic cables andmicrofocusing lens to impinge on opposite surfaces of a rotatingsubstrate. The use of a fiber optic cable delivery system facilitatesalignment and reduces maintenance, even in geographical areas subject toenvironmental changes, particularly seismological disturbances. Incopending application Ser. No. 08/955,448 filed on Oct. 21, 1997 anapparatus and methodology is disclosed wherein inherent variations inthe surface topography of a disk substrate, such as variations insurface planarity, e.g., surface runout, are detected and a laserparameter adjusted in response to the detected surface variation. Suchcontrolled texturing parameters include laser power, pulse duration,repetition rate and/or the distance between the microfocusing lens andthe substrate surface.

Thus, conventional practices in texturing a substrate, e.g., anon-magnetic substrate or underlayer provided thereon, comprisedecoupling the magnetic requirements (data zone on which information isrecorded and read) from the mechanical requirements (landing zone), byforming a dedicated landing zone where the slider is parked and latchedafter the drive has been shut down. Baumgart et al. “Safe landings:Laser texturing of high-density magnetic disks” Data Storage, March1996; U.S. Pat. No. 5,550,696 issued to Nguyen; and U.S. Pat. No.5,595,791 issued to Baumgart et al. Accordingly, laser texturing hasbeen employed to provide a landing zone having a topographical profilecomprising a plurality of spaced apart protrusions extending above thesubstrate surface or a plurality of spaced apart depressions extendinginto the substrate surface. Typically, such laser texturing to provide alanding zone is performed on a non-magnetic substrate which haspreviously been polished by the substrate manufacturer to provide aspecular or smooth surface which serves as the data zone.

Lasers have also been employed to inscribe a plurality of indeliblegrooves in a surface of a magnetic recording medium to function asoptical servo tracks. Williams et al. U.S. Pat. No. 5,120,927. Lasertechniques have also been employed to remove particular contaminationfrom surfaces. Tam, “Laser-cleaning techniques for removal of surfaceparticulates”, J. Appl. Phys. 71 (7), Apr. 1, 1992, pp. 3515-3523.

It is recognized that the most significant magnetic properties ofthin-film media are the remanence-thickness product (M_(r)t), coercivity(H_(c)) and coercive squareness (S_(*)) . The concept of orientationratio (OR) has been defined for magnetic media as a means to quantifyand understand the directional nature of magnetic properties of amagnetic recording medium. Thus, the most common definition of OR is theratio of M_(r)t, H_(c) or S_(*) in the tangential direction to values inthe radial direction. Thus, in-plane anisotropies impact the OR for aparticular magnetic recording medium including scratch. anisotropies.Thus, the mechanism for the OR results from a geometric effect and isbased upon the preferential growth of crystallite chains due to aself-shadowing mechanism stemming from mechanical polishing. Johnson etal., “In-Plane Anisotropy in Thin-Film Media: Physical Origins ofOrientation Ratio (Invited)”, IEEE Transactions on Magnetics, Vol. 31,No. 6, November 1995, pp. 2721-2727.

Circumferential polishing or texturing of rigid disk substrates providesanisotropy in thin film magnetic disks which enhances coercivity in thetrack direction. The orientation in textured or polished thin film diskscan be generated by magnetostatic effects arising from effectivedecoupling in the cross track direction. Such magnetostatic anisotropyincreases in strength as the polishing grooves become finer and deeper.This effect is stronger where there is chain growth along the trackdirection. Miles et al., “Micromagnetic Simulation of Texture InducedOrientation in Thin Film Media”, IEEE Transactions on Magnetics, Vol.31, No. 6, November 1995, pp. 2770-2772.

As the requirements for high areal recording density increase, the needfor improved substrate texturing for inducing magnetic orientation in adata zone increases. Such improved texturing requires fine, deep anduniform scratches which cannot be achieved employing conventionalmechanical polishing techniques. Accordingly, there exists a need forimproved methodology for texturing a non-magnetic substrate orunderlayer thereon of a magnetic recording medium to provide a data zonewith precisely formed uniform topographies to induce the requisitemagnetic orientation in a subsequently applied magnetic layer.

DISCLOSURE OF THE INVENTION

An object of the present invention is a method and apparatus foruniformly texturing a data zone on a substrate for a magnetic recordingmedium.

Another object of the present invention is a method and apparatus forlaser texturing a data zone and a landing zone on a substrate for a highareal recording density magnetic recording medium.

A further object of the present invention is a magnetic recording mediumcomprising a laser textured data zone.

Another object of the present invention is a magnetic recording mediumcomprising a laser textured data zone and a laser textured landing zone.

Additional objects, advantages and other features of the invention willbe set forth in each description which follows and in part will becomeapparent to those having ordinary skill in the art upon examination ofthe following or may be learned from the practice of the invention. Theobjects and advantages of the invention may be realized and obtained asparticularly pointed out in the appended claims.

According to the present invention, the foregoing and other objects areachieved in part by a magnetic recording medium comprising a landingzone and a laser textured data zone formed on a surface thereof.

Another aspect of the present invention is a magnetic recording mediumhaving a substrate surface comprising a laser textured data zonecontaining a plurality of substantially uniform concentric microgroovesand a laser textured landing zone containing a plurality ofsubstantially uniform protrusions or depressions.

A further aspect of the present invention is a method of manufacturing amagnetic recording medium, which method comprises: laser texturing asurface of a rotating substrate to form a laser textured data zone.

Another aspect of the present invention is a method of manufacturing amagnetic recording medium, which method comprises: impinging acontinuous wave laser on a rotating substrate surface to form a lasertextured data zone comprising uniform concentric microgrooves; andimpinging a pulsed laser light beam on the substrate surface to form alaser textured landing zone comprising a plurality of substantiallyuniform protrusions or depressions.

A further aspect of the present invention is an apparatus for lasertexturing a substrate for a magnetic recording medium, which apparatuscomprises: a spindle for rotating a substrate during laser texturing; asource for emitting a continuous wave laser beam; and a microfocusinglens system positioned proximate a surface of the substrate throughwhich the continuous wave laser is impinged on the rotating substratesurface to laser texture a data zone.

Additional objects and advantages of the present invention will becomereadily apparent to those skilled in this art from the followingdetailed description, wherein embodiments of the invention aredescribed, simply by way of illustration of the best mode contemplatedfor carrying out the invention. As will be realized, the invention iscapable of other and different embodiments, and its several details arecapable of modifications in various obvious respects, all withoutdeparting from the invention. Accordingly, the drawings and descriptionare to be regarded as illustrative in nature, and not as restrictive.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates a data zone laser texturing apparatus in accordancewith an embodiment of the present invention.

FIG. 2 illustrates another laser texturing apparatus in accordance withan embodiment of the present invention.

FIG. 3 illustrates an orthogonal microfocusing lens array in accordancewith an embodiment of the present invention.

FIG. 4 illustrates a rectangular array of microfocusing lenses inaccordance with an embodiment of the present invention.

DESCRIPTION OF THE INVENTION

Conventional magnetic recording media typically comprise a non-magneticsubstrate having sequentially formed on opposite surfaces thereof one ormore underlayers, a magnetic layer, a protective overcoat, typicallycontaining carbon, and a lubricant topcoat. The non-magnetic substrateor an underlayer formed thereon is typically textured to form a landingzone, as by impinging a pulsed laser light beam thereon during substraterotation to form a plurality of uniformly spaced apart protrusions ordepressions, while the data zone typically comprises a polished specularsurface. For example, a conventional aluminum alloy substrate, such asaluminum-magnesium substrate having an amorphous nickel-phosphorous(NiP) plating thereon is commercially available with a specular surface.The specular surface is textured to form the landing zone while theremaining polished specular surface functions as the data zone. The datazone can also comprise a plurality of scratches formed by mechanicalpolishing during substrate rotation for inducing magnetic orientation inthe subsequently deposited magnetic layer. The minute polishingscratches in the data zone imparted by circumferential polishingproduces in-plane isotropy enhancing coercivity (H_(c)) and impacting(M_(r)t) and S_(*). These properties must be optimized for high arealrecording density, thereby requiring formation of data zone microtexturewith greater precision and uniformity.

In accordance with the present invention, a data zone having highprecision and uniformity is achieved by laser texturing. In anembodiment of the present invention, a continuous wave laser light beamis impinged on a rotating substrate surface, the substrate constitutingeither the non-magnetic substrate or the non-magnetic substrate havingone or more underlayers thereon. The continuous wave laser light beamcan be derived from a yttrium-aluminum-garnet (YAG),yttrium-lithium-fluoride (YLF) or yttrium-vanadium-oxide (YVO₄) laserlight beam source. The continuous wave laser light beam is passedthrough a microfocusing lens system and impinged on a rotating substratesurface to laser texture a data zone to provide a suitablemicrotopography for orientation of a subsequently deposited magneticlayer, such as a microtopography comprising a plurality of substantiallyuniform concentric microgrooves, with high precision.

In another embodiment of the present invention, a pulsed laser lightbeam is impinged on a rotating substrate surface or underlayer thereon,at a sufficiently high repetition rate to form a microtopographycomprising a plurality of substantially uniform concentric microgrooveswith substantially high precision, as in the embodiment employing acontinuous wave laser light beam. For example, a pulsed laser light beamhaving a repetition rate of about 300 KHz to about 500 KHz providessubstantially uniform concentric microgrooves. The use of such a highrepetition rate provides a pulse laser width of about 100 nanoseconds toabout 300 nanoseconds.

The microgrooves formed in accordance with the present inventionemploying a continuous wave laser light beam are uniform and precise andcan be formed in fine patterns for improved areal recording density. Inembodiments of the present invention, the microgrooves are spaced apartby a distance less than about 1.0 μm, e.g., less than about 0.5 μm.Typically, the spacings and dimensions of the microgrooves do not varymore than 10% among microgrooves. In embodiments of the presentinvention, microgrooves are formed having a width of about 0.2 μm toabout 0.8 μm and a depth extending into the substrate surface a distanceof about 10 Å to about 50 Å. The uniformity and precision of the lasertextured data zones of the present invention provides optimum in-planeisotropies and OR, thereby achieving an M_(r)t of about 0.5 to about 1.2and H_(c) of about 2,500 to about 5,000.

Embodiments of the present invention comprise passing a continuous wavelaser light beam through a fiber optic cable, e.g., a single mode fiberoptic cable, and then through the microfocusing lens system to impingeon the rotating substrate surface to form a laser textured data zonecomprising a plurality of substantially uniform concentric microgrooves.A microfocusing lens system found suitable in the practice of thepresent invention comprises a bundle of fiber optic cables, each fiberoptic cable linked to a microfocusing lens. The microfocusing lenses arearranged in an orthogonal array comprising a plurality of horizontallyspaced microfocusing lenses and a plurality of vertically spaced apartmicrofocusing lenses. It has been found particularly suitable to employa microfocusing lens system comprising a plurality of microfocusinglenses horizontally spaced apart by a distance of about 10 μm to about2,000 μm and a plurality of microfocusing lenses vertically spaced apartby a distance of about 10 μm to about 300 μm.

The present invention can be implemented in combination with lasertechnology for laser texturing a landing zone. Such landing zone lasertechnology typically comprises impinging a pulsed laser light beam on arotating substrate surface to create a topography comprising a pluralityof substantially uniform spaced apart protrusions or depressions.Embodiments of the present invention comprise effectively decoupling themagnetic aspects from the mechanical aspects of a magnetic recordingmedium by laser texturing a substrate surface to provide a data zonecomprising a plurality of uniformly spaced apart microgrooves and aseparate laser textured landing zone which typically comprises aplurality of protrusions having a diameter of about 2 μm to about 8 μm,a height of about 60 Å to about 200 Å and a spacing of about 10 μm toabout 50 μm.

As in conventional practices, a magnetic recording medium produced inaccordance with the present invention comprises, sequentially, anon-magnetic substrate, at least one underlayer formed on opposite sidesthereof, at least one magnetic layer formed on the underlayer, aprotective overcoat formed on the magnetic layer and a lubricant topcoatformed on the protective overcoat. In accordance with embodiments of thepresent invention, the non-magnetic substrate or underlayer thereon islaser textured to form the data zone and landing zone, which textureddata zone and landing zone are substantially reproduced on layerssubsequently deposited thereon.

In practicing the present invention, the landing zone can be texturedemploying the apparatus and methodology disclosed in copendingapplication Ser. No. 08/954,585 filed on Oct. 20, 1997 now U.S. Pat. No.5,952,058, which apparatus and methodology comprises a fiber optic cablelaser delivery system for optimum maintenance, and/or employing theapparatus and methodology disclosed in copending application Ser. No.08/955,448 filed on Oct. 21, 1997, which apparatus and methodologycomprises fiber optic probes and a data processing and a control systemfor detecting variations in surface planarity and controlling a lasertexturing parameter in response to the detected surface variation tomaintain uniform precision during laser texturing.

Embodiments of the present invention comprise providing an opticalprobe, e.g., a fiber optic probe, in proximity to the surface of arotating substrate surface during laser texturing, as disclosed incopending application Ser. No. 08/955,448 filed on Oct. 21, 1997. Insuch embodiments, the fiber optic probe detects surface variations,including subtle variations in planarity, e.g., inherent surfacewaviness or runout. Light signals indicative of any such surfacevariations are fed back to an optical feedback data processing andcontrol system wherein the light signals are converted into electricalsignals in an associated interface module housed therein, the dataanalyzed and a laser parameter and/or the distance between amicrofocusing lens or a microfocusing lens array and the substratesurface adjusted. The optical feedback data processing and controlsystem contains an associated computer and a laser controller linked toa continuous wave laser light beam source and a pulsed laser light beamsource. The laser optic systems comprise an automatic attenuator forappropriate adjustment of the power of the laser light beam in responseto sensed surface variations to ensure uniform laser texturing. Thedistance between the microfocusing lens for laser texturing the landingzone and the substrate surface, and the distance between themicrofocusing lens array for laser texturing the data zone and thesubstrate surface can also be adjusted in response to a detected surfacevariation, in lieu of or in addition to adjusting a laser parameter, toinsure uniform laser texturing of the data zone and landing zone. Thedistance between the microfocusing lens array or microfocusing lens andsubstrate surface can be varied using conventional means, such as athrough-the-lens autofocus optical system, a capacitance probe distancedetector or other proximate control device.

Thus, embodiments of the present invention include positioning amicrofocusing lens and a microfocusing lens array at a distance of about500 μm to about 1,500 μm from opposite surfaces of a substrate on arotating spindle. Optical probes, such as fiber optic probes, arepositioned proximate opposite surfaces of the substrate during data andlanding zone laser texturing to detect surface variations, such assurface planarity variations stemming from inherent waviness or surfacerunout. The fiber optic probes are linked to an optical feedback dataprocessing and control system comprising a fiber optic probe-interfacemodule, a processor with associated conventional peripheral equipmentand laser controller for adjusting a relevant data or landing zone lasertexturing parameter in response to a detected surface variation. Theoptical feedback data processing and control system can also comprise amechanism controller linked to the microfocusing lenses andmicrofocusing lens arrays for adjusting the distance between eachmicrofocusing lens and microfocusing lens array and opposite substratesurfaces and, hence, the focus to maintain uniform precision duringtexturing. Upon detecting an elevation, the laser power can be reducedor discontinued in response thereto or the distance between themicrofocusing lens array and substrate surface increased in lasertexturing the data zone. The pulse duration and repetition rate can beadjusted in response to a detected surface variation in combination withthe power and/or distance between the microfocusing lens and substratesurface in laser texturing the landing zone. For example, upon detectinga surface elevation, the pulse duration can be reduced, the repetitionrate reduced and/or the distance between the substrate and amicrofocusing lens increased.

An apparatus in accordance with an embodiment of the present inventionis illustrated in FIG. 1. Laser light beam 11 is passed from continuouswave laser light beam source 10, e.g., a YAG laser source, to beamexpander 12, through aperture 12 and then through microfocusing lens 14to impinge on a surface of substrate 15 rotated on spindle 16 indirection of arrow A. The impinging continuous wave laser light beamtextures the rotating substrate surface to form a laser textured datazone comprising a plurality of concentric microgrooves with highprecision and uniformity.

In the embodiment depicted in FIG. 1, a fiber optic probe 17 ispositioned proximate rotating substrate 15. Fiber optic probe 17 islinked by fiber optic cable 18 to an optical feedback data processingand control system comprising processor 19 and peripheral terminal 100via 101. Processor 19 is also linked to laser controller 104 via 103,while laser controller 104 is linked to laser light beam source 10 via105. Processor 19 also includes displacement mechanism controller 106 aspart of the optical feedback data processing and control system.Displacement mechanism control 106 is linked to microfocusing lens array14 via 102. Upon detection of a surface variation by fiber optic probe17, the laser power and/or distance between microfocusing lens system 14and substrate surface 15 is adjusted to ensure laser texturing the datazone with high precision and uniformity.

Another embodiment of the present invention is illustrated in FIG. 2,and includes elements for laser texturing decoupled data and landingzones. Substrate surface 20 is rotated on spindle 21 in direction ofarrow B. Data zone D is laser textured employing microfocusing lenssystem 22 comprising a plurality of microfocusing lenses through which acontinuous wave laser light beam is impinged to form a plurality ofsubstantially uniform concentric microgrooves on rotating substratesurface 20. Each microfocusing lens of the microfocusing lens system iscoupled to an optical fiber of a bundle (not shown) within multileveloptical fiber coupling 24. Fiber optic cable 23 optically linksmultilevel optical fiber coupling 24 to a continuous wave laser lightbeam.

In the embodiment depicted in FIG. 2, a landing zone is also lasertextured on rotating substrate surface 20 by impinging a pulsed laserlight beam thereon through microfocusing lens 26 optically linked tofiber optic cable 27 via fiber optic coupling 28 and snap-on columnator29. Focused continuous wave laser light beams 25 impinge on rotatingsubstrate 20 to laser texture a data zone comprising a plurality ofsubstantially uniform concentric grooves, while focused pulsed laserlight beam 201 impinges on rotating substrate 20 to laser texture alanding zone comprising a plurality of substantially uniform spacedapart protrusions.

In the embodiment depicted in FIG. 2, a fiber optic probe 202 ispositioned proximate rotating substrate surface 20 for detecting asurface variation. Fiber optic probe 202 is linked via fiber optic cable203 to an optical feedback data processing and control system comprisingprocessor 205 and peripheral terminal 206 via 207. Processor 205 islinked to laser controller 208 via 209, while laser controller 208 islinked via 210 to a continuous wave laser light beam source forcontrolling the laser light beam power in response to a surfacevariation detected by fiber optic probe 202. Laser control 201 is alsolinked via 211 to a pulsed laser light beam source for adjusting a lasertexturing parameter in response to a surface variation detected by fiberoptic probe 202. Processor 205 also includes displacement mechanismcontroller 204 linked to microfocusing lens array 22 via 212 foradjusting the distance between microfocusing lens system 22 and rotatingsubstrate surface 20 in response to a surface variation detected byfiber optic probe 202. Displacement mechanism controller 204 is alsolinked to microfocusing lens 29 via 211 for adjusting the distancebetween microfocusing lens 209 and rotating substrate surface 20 inresponse to a surface variation detected by fiber optic probe 202.

The microfocusing lens array 22 employed in the present invention cancomprise a fiber optic bundle within housing 30, each fiber optic cableleading to a microfocusing lens 31. In the embodiment depicted in FIG.3, the microfocusing lenses of the microfocusing lens array are arrangedin an array comprising a plurality of microfocusing lenses substantiallyhorizontally spaced apart by a distance X of about 500 μm to about 2,000μm and a plurality of microfocusing lenses substantially verticallyspaced apart by a distance Y of about 100 μm to about 300 μm. In anotherembodiment of the present invention, as shown in FIG. 4, themicrofocusing lens array comprises a substantially rectangular array ofsubstantially horizontally spaced apart microfocusing lenses andsubstantially vertically spaced apart microfocusing lenses, by a similardistance d, e.g., about 10 μm to about 50 μm.

Embodiments of the present invention involve the use of conventionalcomponents which are commercially available. For example, the fiberoptical probes employed in the present invention can be obtained fromMTI located in Lantham, N.Y. The fiber optic probes for use in thepresent invention can also comprise a plurality of light transmittingfibers and a plurality of light receiving fibers. See, for example,Kissinger et al., “Fiber-Optic Probe Measures Runout of Stacked Disks”,July-August 1997 Data Storage, pages 79-84. The use of control systemsfor responding to detected surface variations has previously beenemployed. See, for example, Muranushi et al., U.S. Pat. No. 5,153,785,the entire disclosure of which is incorporated herein by reference.

In practicing the present invention, the substrate can be any substratetypically employed in the manufacture of magnetic recording media, suchas a metal substrate or an alternate substrate comprising a glass,ceramic or glass-ceramic material or such as O'Hara, Hoya and Nipponglass. Other conventional substrates include aluminum alloy substrateswith a coating thereon, such as nickel-phosphorous. It has been foundsuitable to employ a CO₂ laser when texturing a glass, ceramic orglass-ceramic substrate, and YLF, YVO₄, and YAG lasers when texturing aNiP or metal substrate.

As one having ordinary skill in the art would recognize, conventionalpractices in manufacturing a magnetic recording medium comprisetexturing opposite surfaces of a substrate and depositing a plurality oflayers thereon. As one having ordinary skill in the art would alsorecognize, after laser texturing opposite substrate surfaces inaccordance with the present invention, conventional layers are depositedthereon to complete the magnetic recording medium. For example, variousconventional magnetic recording media comprise sequentially sputterdeposited layers on the substrate, such as an underlayer, magnetic alloylayer and protective overcoat. A lubricant topcoat is alsoconventionally applied to the protective topcoat.

The magnetic layers deposited in accordance with the present inventioncan be any of those conventionally employed in the production ofmagnetic recording media. Such conventional magnetic alloys, include,but are not limited to, cobalt (Co) alloys, such as Co-base alloys,e.g., cobalt-chromium (CoCr), cobalt-samarium (CoSm),cobalt-chromium-tantalum (CoCrTa), cobalt-nickel-chromium (CoNiCr),cobalt-chromium-samarium (CoCrSm), cobalt-chromium-platinum-tantalum(CoCrPtTa), cobalt-chromium-platinum (CoCrPt), cobalt-nickel-platinum(CoNiPt), cobalt-nickel-chromium-platinum (CoNiCrPt) andcobalt-chromium-platinum-boron (CoCrPtB) . The thickness of the magneticlayer is consistent with conventional practices and manufacturing amagnetic recording medium. Cobalt-base alloys having a thickness ofabout 100 Å to about 1000 Å, such as 200 Å to about 500 Å, has beenfound suitable.

As in conventional practices, one or more underlayers can be depositedon the textured substrate prior to depositing the magnetic layer. Theunderlayer can comprise chromium or a chromium-alloy, such aschromium-vanadium or chromium-titanium, oxygen-doped chromium, tungstenor a tungsten alloy.

In addition, a protective overcoat, such as a carbon overcoat, can bedeposited on the magnetic layer, and a lubricant topcoat deposited onthe protective overcoat. The underlayer, magnetic layers and protectiveovercoat can be applied in a conventional manner, by any of varioussputtering techniques, deposited in conventional thicknesses employed inproduction of magnetic recording media.

The present invention can be employed to produce any of various types ofmagnetic recording media, including thin film disks, with an attendantimprovement in flying stability, glide performance and head-mediuminterface reliability. The present invention advantageously enablesuniform precise laser texturing of a data zone of a magnetic recordingmedium to provide concentric microgrooves. In addition, the presentinvention also enables simultaneous laser texturing of a landing zonecomprising a plurality of substantially uniform spaced apart protrusionsor depressions, thereby effectively providing decoupling between themagnetic and mechanical characteristics of their magnetic recordingmedium. The present invention enables the production of high arealrecording density magnetic recording media exhibiting optimized in-planeanisotropies and OR. The present invention can be employed to produceany of various types of magnetic recording media, particularly highareal recording density magnetic recording media.

Only the preferred embodiment of the invention and but a few examples ofits versatility are shown and described in the present invention. It isto be understood that the invention is capable of use in various othercombinations and environments and is capable of changes or modificationswithin the scope of the inventive concept as expressed herein.

What is claimed is:
 1. A method of manufacturing a magnetic recordingmedium, which method comprises laser texturing a surface of a rotatingsubstrate to form a laser textured data zone on which information isrecorded and stored, the laser textured data zone comprising a pluralityof concentric microgrooves suitable for orientation of a subsequentlydeposited magnetic layer.
 2. The method according to claim 1, comprisinglaser texturing opposite surfaces of the substrate to form a lasertextured data zone thereon.
 3. The method according to claim 2,comprising laser texturing opposite surfaces of a rotating non-magneticsubstrate to form a laser textured landing zone and a laser textureddata zone on each surface; and depositing sequentially thereon: at leastone underlayer; a magnetic layer; a protective overcoat; and a lubricanttopcoat; wherein, the laser textured data zone and the laser texturedlanding zone are substantially reproduced in the subsequently depositedlayers.
 4. The method according to claim 1, comprising impinging a highrepetition rate pulsed laser light beam on the rotating substratesurface to form the laser textured data zone.
 5. The method according toclaim 4, comprising impinging a pulsed laser light beam at a repetitionrate of about 300 KHz to about 500 KHz on the rotating substrate surfaceto laser texture the data zone by forming a plurality of substantiallyuniform concentric microgrooves.
 6. The method according to claim 4,wherein the high repetition rate laser light beam has a repetition rateof about 300 KHz to about 500 KHz.
 7. A method of manufacturing amagnetic recording medium, which method comprises impinging a continuouswave laser light beam on a rotating substrate surface to form a lasertextured data zone on which information is recorded and stored, thelaser textured data zone comprising a plurality of concentricmicrogrooves suitable for orientation of a subsequently depositedmagnetic layer.
 8. The method according to claim 7, wherein thecontinuous wave laser is derived from a yttrium-aluminum-garnet,yttrium-lithium-fluoride or vanadium-yttrium-oxide laser source.
 9. Themethod according to claim 7, comprising passing the continuous wavelaser light beam through a fiber optic cable and then through amicrofocusing lens system to impinge on the rotating substrate surfaceto laser texture the data zone.
 10. The method according to claim 9,wherein the microfocusing lens system comprises a bundle of fiber opticcables, each fiber optic cable linked to a microfocusing lens.
 11. Themethod according to claim 10, wherein the plurality of microfocusinglenses are arranged in a substantially rectangular array ofsubstantially horizontally spaced apart microfocusing lenses by adistance of about 10 μm to about 50 μm and substantially verticallyspaced apart microfocusing lenses by substantially the same distance ofabout 10 μm to about 50 μm.
 12. The method according to claim 10,wherein the plurality of microfocusing lenses are arranged in an arraycomprising a plurality of horizontally spaced apart microfocusing lensesand a plurality of vertically spaced apart microfocusing lenses.
 13. Themethod according to claim 12, wherein the plurality of microfocusinglenses are horizontally spaced apart by a distance of about 10 μm toabout 2,000 μm; and a plurality of microfocusing lenses are verticallyspaced apart by a distance of about 10 μm to about 300 μm.
 14. A methodof manufacturing a magnetic recording medium, which method compriseslaser texturing a rotating substrate surface to form a laser textureddata zone on which information is recorded and stored, the lasertextured data zone comprising a plurality of substantially uniformconcentric microgrooves suitable for orientation of a subsequentlydeposited magnetic layer.
 15. The method according to claim 14, whereineach microgroove has a width of about 0.2 μm to about 0.8 μm and extendsinto the surface to a depth of about 10 Å to about 50 Å.
 16. The methodaccording to claim 14, wherein the microgrooves are spaced apart by adistance of less than about 1.0 μm.
 17. The method according to claim16, wherein the microgrooves are spaced apart by a distance of less thanabout 0.5 μm.
 18. A method of manufacturing a magnetic recording medium,which method comprises: laser texturing a surface of a rotatingsubstrate to form a laser textured data zone on which information isrecorded and stored, the laser textured data zone comprising a pluralityof concentric microgrooves suitable for orientation of a subsequentlydeposited magnetic layer; and impinging a pulsed laser light beam on therotating substrate surface to form a laser textured landing zonecomprising a plurality of substantially uniform spaced apart protrusionsor depressions during laser texturing the data zone.
 19. The methodaccording to claim 18, comprising impinging the pulsed laser light beamon the rotating substrate surface to form a laser textured landing zonecomprising a plurality of protrusions having a diameter of about 2 μm toabout 8 μm, a height of about 60 Å to about 200 Å and a spacing of about10 μm to about 50 μm.
 20. The method according to claim 18, furthercomprising: detecting a variation in the planarity of the substratesurface undergoing laser texturing; and controlling a laser texturingparameter for laser texturing the data zone in response to the detectedsurface variation.
 21. The method according to claim 20, comprisingdetecting the variation in planarity with a fiber optic probe.
 22. Themethod according to claim 20, comprising adjusting any or a combinationof the laser power and distance between the microfocusing lens array andsubstrate surface in response to a detected surface variation in lasertexturing the data zone.
 23. The method according to claim 22, furthercomprising adjusting any or a combination of the laser power, laserpulse duration, laser repetition rate and distance between themicrofocusing lens and substrate surface in response to a detectedsurface variation in laser texturing the landing zone.
 24. A method ofmanufacturing a magnetic recording medium, the method comprising passinga continuous wave laser light beam through a fiber optic cable and thenthrough a microfocusing lens system to impinge on a rotating substratesurface to laser texture a data zone, wherein the microfocusing lenssystem comprises a bundle of fiber optic cables, each fiber optic cablelinked to a microfocusing lens; and the plurality of microfocusinglenses are horizontally spaced apart by a distance of about 10 μm toabout 2,000 μm; and a plurality of microfocusing lenses are verticallyspaced apart by a distance of about 10 μm to about 300 μm.
 25. A methodaccording to claim 24, wherein the horizontally spaced apartmicrofocusing lenses are spaced apart by a distance of about 10 μm toabout 50 μm and the vertically spaced apart microfocusing lenses arespaced apart by substantially the same distance of about 10 μm to about50 μm.
 26. A method of manufacturing a magnetic recording medium, themethod comprising laser texturing a rotating substrate surface to form alaser textured data zone comprising a plurality of substantially uniformconcentric microgrooves spaced apart by a distance of less than about1.0 μm.
 27. A method of manufacturing a magnetic recording medium, themethod comprising: laser texturing a surface of a rotating substrate toform a laser textured data zone; impinging a pulsed laser light beam onthe rotating substrate surface to form a laser textured landing zonecomprising a plurality of protrusions having a diameter of about 2 μm toabout 8 μm, a height of about 60 Å to about 200 Å and a spacing of about10 μm to about 50 μm; detecting a variation in the planarity of thesubstrate surface undergoing laser texturing with a fiber optic probe;and controlling a laser texturing parameter for laser texturing the datazone in response to the detected surface variation.
 28. A method ofmanufacturing a magnetic recording medium, the method comprisingimpinging a high repetition rate pulsed laser light beam on a rotatingsubstrate surface to form a laser textured data zone, wherein the highrepetition rate laser light beam has a repetition rate of about 300 KHzto about 500 KHz.
 29. The method according to claim 28, comprisingimpinging the pulsed laser light beam at a repetition rate of about 300KHz to about 500 KHz on the rotating substrate surface to laser texturethe data zone by forming a plurality of substantially uniform concentricmicrogrooves.